// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_RENDERER_MEDIA_WEBAUDIO_MEDIA_STREAM_SOURCE_H_
#define CONTENT_RENDERER_MEDIA_WEBAUDIO_MEDIA_STREAM_SOURCE_H_

#include <memory>

#include "base/time/time.h"
#include "content/renderer/media/media_stream_audio_source.h"
#include "media/base/audio_bus.h"
#include "media/base/audio_push_fifo.h"
#include "third_party/WebKit/public/platform/WebAudioDestinationConsumer.h"
#include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
#include "third_party/WebKit/public/platform/WebVector.h"

namespace content {

// Implements the WebAudioDestinationConsumer interface to provide a source of
// audio data (i.e., the output from a graph of WebAudio nodes) to one or more
// MediaStreamAudioTracks. Audio data is transported directly to the tracks in
// 10 ms chunks.
class WebAudioMediaStreamSource final
    : NON_EXPORTED_BASE(public MediaStreamAudioSource),
      public blink::WebAudioDestinationConsumer {
public:
    explicit WebAudioMediaStreamSource(blink::WebMediaStreamSource* blink_source);

    ~WebAudioMediaStreamSource() override;

private:
    // WebAudioDestinationConsumer implementation.
    //
    // Note: Blink ensures setFormat() and consumeAudio() are not called
    // concurrently across threads, but these methods could be called on any
    // thread.
    void setFormat(size_t number_of_channels, float sample_rate) override;
    void consumeAudio(const blink::WebVector<const float*>& audio_data,
        size_t number_of_frames) override;

    // Called by AudioPushFifo zero or more times during the call to
    // consumeAudio().  Delivers audio data with the required buffer size to the
    // tracks.
    void DeliverRebufferedAudio(const media::AudioBus& audio_bus,
        int frame_delay);

    // MediaStreamAudioSource implementation.
    bool EnsureSourceIsStarted() final;
    void EnsureSourceIsStopped() final;

    // In debug builds, check that all methods that could cause object graph
    // or data flow changes are being called on the main thread.
    base::ThreadChecker thread_checker_;

    // True while this WebAudioMediaStreamSource is registered with
    // |blink_source_| and is consuming audio.
    bool is_registered_consumer_;

    // A wrapper used for providing audio to |fifo_|.
    std::unique_ptr<media::AudioBus> wrapper_bus_;

    // Takes in the audio data passed to consumeAudio() and re-buffers it into 10
    // ms chunks for the tracks. This ensures each chunk of audio delivered to
    // the tracks has the required buffer size, regardless of the amount of audio
    // provided via each consumeAudio() call.
    media::AudioPushFifo fifo_;

    // Used to pass the reference timestamp between DeliverDecodedAudio() and
    // DeliverRebufferedAudio().
    base::TimeTicks current_reference_time_;

    // This object registers with a blink::WebMediaStreamSource. We keep track of
    // that in order to be able to deregister before stopping this source.
    blink::WebMediaStreamSource blink_source_;

    DISALLOW_COPY_AND_ASSIGN(WebAudioMediaStreamSource);
};

} // namespace content

#endif // CONTENT_RENDERER_MEDIA_WEBAUDIO_MEDIA_STREAM_SOURCE_H_
